The present invention relates generally to the assembly of transmissions to be employed in vehicular powertrains. More particularly, the present invention relates to the assembly of transmissions of various types from modular components. Specifically, the present invention relates to vehicular transmissions that can be assembled from a modular housing assembly, a modular input assembly and a modular output assembly that are selected from several such available assemblies such that the resulting transmission may be tailored to predetermined operational parameters, i.e., to the specific use, or uses, to which the vehicle in which that transmission will be incorporated is to be primarily employed.
The purpose of a vehicular powertrain is to transmit the power delivered by an internal combustion engine, and/or an electric motor, to the output drive shaft emanating from the transmission. Transmissions typically provide a neutral, at least one reverse and one or more forward driving ranges that impart power from an engine, and/or other power sources, to the drive members that deliver the tractive effort from the vehicle to the terrain over which the vehicle is being driven. As such, the drive members may be front wheels, rear wheels or a track, as required to provide the desired performance.
Although a wide variety of transmission types are known to the art that are capable of receiving the output power from either an engine or an electric motor, or both, in order to operate at high efficiencies during various operating conditions, no single transmission configuration is most favorable for all operating conditions.
It is, therefore, the intent of the present invention to provide a means by which the manufacturer of vehicular transmissions can vary the selection of interfitting modular components in order to facilitate the ease of assembly and reduce the costs of manufacturing various transmission permutations in order to accommodate the operating parameters of vehicles in which the transmissions are to be employed.
For example, it may be desired, if not required, that some vehiclesxe2x80x94such as transit busesxe2x80x94operate at a high average speed. To the contrary, other vehiclesxe2x80x94such as shuttle busesxe2x80x94operate at low average speeds. Hence, the manufacturer of such vehicles is faced with the dilemma that no one prior art transmission is most efficiently adapted to accommodate both desired operating parameters. For example, the low average speed shuttle bus has a low power consumption as compared to the high average transit vehicle, and the shuttle bus is typically required to make many more stops during its normal operating cycle. In addition, the shuttle bus often operates in geographic locations where emissions must comport with stringent environmental considerations. The usage of electrical energy to power such vehicles can be a significant plus inasmuch as the use of electrical energy to power a vehicle accommodates not only environmental restrictions but also numerous start/stop cycles. To employ comparable storage and usage of electrical energy as the sole source of energy for transit buses, however, might well be uneconomical, even though using only an internal combustion engine would very likely result in an undesirable higher emissions output. Hence, in some circumstances, it may be desirable to utilize a simple series generator-motor combination with which an onboard internal combustion engine may be selectively employed solely to charge a device for storing electrical energy.
By and large, therefore, the vast majority of vehicular, operational parameters can be satisfied by selecting a transmission from a group of transmission types, such as: a simple xe2x80x9cseriesxe2x80x9d generator-motor assembly that does not include a mechanical path between the internal combustion engine and the transmission output shaft; a single-mode, input-split transmission; a single-mode, compound-split transmission; and a dual-mode, compound-split transmission. All of the foregoing transmission types are well known to those skilled in this art, but heretofore it has not been convenient selectively to construct any one of the foregoing transmission types from a plurality of modular assembliesxe2x80x94viz.: from a selected housing assembly comprised of a common housing sub-assembly and a selected central shaft sub-assembly; a selected input assembly; and a selected output assembly.
It is, therefore, one primary aspect of the present invention to provide a new and novel modular technique for assembling a family of vehicular transmissions, including a simple xe2x80x9cseriesxe2x80x9d generator-motor assembly that does not include a mechanical path between the internal combustion engine and the transmission output shaft; a single-mode, input-split transmission; a single-mode, compound-split transmission; and a dual-mode, compound-split transmission.
It is another aspect of the present invention to provide a modular assembly technique, as above, wherein three assemblies are required selectively to fabricate any one of the aforesaid family of transmissionsxe2x80x94the assemblies including a plurality of housing assemblies, a pair of input assemblies and a plurality of output assemblies as well as a choice of one from at least two central shaft sub-assemblies operatively received within a common housing sub-assembly.
It is a further aspect of the present invention to provide a modular assembly technique, as above, whereby even the modular assemblies may comprise a plurality of modular components which may be employed in more than one assembly variation.
These and other aspects of the invention, as well as the advantages thereof over existing and prior art forms, which will be apparent in view of the following detailed specification, are accomplished by means hereinafter described and claimed.
By way of a general introductory description, the assembly of a desired electric variable transmission included within a plurality of transmission types can be accomplished by selecting and connecting modular assemblies that have themselves been previously assembled in conformity with the concepts of the present invention.